1. Field of the Invention
The present invention relates to a photoelectric conversion element, a solar battery, and a photo sensor.
2. Description of the Related Art
As a photoelectric conversion element and a solar battery having the photoelectric conversion element which convert an optical energy into an electrical energy, a single crystalline silicon solar battery as a first generation, a polycrystalline silicon solar battery formed of a number of crystals as a second generation, and a compound semiconductor solar battery using gallium arsenic and the like as a third generation have been suggested, although they have many problems in cost and the like. In view of this, a solar battery formed of an organic semiconductor is suggested.
An organic semiconductor solar battery is typically a dye thin film solar battery and a dye-sensitization solar battery. A dye thin film solar battery has a p-n heterojunction structure using a perylene derivative as an n-type dye and copper phthalocyanine as a p-type dye.
On the other hand, a dye-sensitization solar battery is called a fourth generation battery and is actively being researched as a photoelectric conversion element which is inexpensive and can provide high conversion efficiency. A dye-sensitization solar battery is a wet type solar battery, in which a semiconductor electrode obtained by adding a photo sensitization dye to porous titanium dioxide thin film so as to be held therein is provided as a work electrode, then the semiconductor electrode is immersed in an electrolyte solution, and an opposite electrode is formed (for example, see Patent Document 1).
A ruthenium complex having an absorption in a visible light region is used as the photo sensitization dye. The electrolyte solution is obtained by adding iodine to a mixture solution of acetonitrile and ethylene carbonate. When the photo sensitization dye is photoexcited, an electron is injected from the photo sensitization dye to a titania semiconductor electrode as the work electrode. On the other hand, a hole oxidizes the electrolyte solution having a hole transporting property and the oxidized electrolyte solution having a hole transporting property receives an electron from the opposite electrode. A solar battery operates by the aforementioned procedure continuously carried out.
The dye sensitization solar battery is different from the p-n heterojunction solar battery in that only an electron is injected to an electrode. Therefore, there are advantages in that a recombination of an electron and a hole does not easily occur and charge separation occurs efficiently. Accordingly, conversion efficiency from an optical energy into an electrical energy exceeds 10%.    [Patent Document 1]    Japanese Patent Laid-Open No. Hei 1-220380